Word: egg
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Mitochondrial DNA is passed down from the mother as part of the egg's genetic contribution. Identical twins, for example, have the same nuclear and mitochondrial DNA, since they're produced when a single egg is fertilized and the resulting embryo splits in two. With a clone, the situation is different. Because the cloning process that Hwang says he used to create Snuppy involves two dogs--one for the nucleus and another for the egg--Snuppy's mitochondrial DNA should not match Tai's. That's what Rhee's scientists say they've found and what Hwang undoubtedly hopes...
Evidently, the risk-taking began in 2004, with Hwang's first major scientific paper on therapeutic cloning. In order to clone an adult, you need to put one of its cells into a human egg cell from which the nucleus has been removed. After electrical fusion and chemical activation, the egg can then start dividing, creating embryonic stem cells. (If left to mature, the embryo could eventually grow into a clone of the original adult--something no reputable scientist would let happen...
...because egg donation is a painful and potentially risky process, paying women to do it is considered a form of coercion. Indeed, the 2004 study said women had "voluntarily donated oocytes ... and no financial reimbursement in any form was paid." But last spring, two of Hwang's researchers let slip to a journalist working for Nature that they had donated their own eggs--which raised questions, since Hwang was their boss, about whether they had been coerced...
...women retracted their story, claiming that their poor English had caused them to misspeak. But by then an aggressive investigative team from MBC, a Korean TV network, had got wind of the allegations. The reporters interviewed many of the egg donors, some of whom said they had not been told they were part of a study, and confirmed that their eggs had been paid for. MBC was also hot on the trail of something even bigger: a tip that Hwang's 2005 Science paper might contain fraudulent data. To verify the allegations, MBC requested samples of the stem cells, which...
...arrive in the lab, at 5 a.m., and rarely left before midnight. He rejected the role of aloof, inaccessible scientist to become a father-like figure for his young charges. And he introduced some genuine innovations into the science of cloning--gently squeezing the nucleus out of a donor egg rather than sucking it out violently and inserting the entire adult cell, not just its nucleus, into the hollowed-out recipient egg. Hwang insisted he had no interest in profiting from his discoveries; indeed, he turned over his patent rights to the university and the government...